function Base64() {
  // private property

  let _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  // public method for encoding

  this.encode = function (input) {

    var output = "";

    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;

    var i = 0;

    input = _utf8_encode(input);

    while (i < input.length) {

      chr1 = input.charCodeAt(i++);

      chr2 = input.charCodeAt(i++);

      chr3 = input.charCodeAt(i++);

      enc1 = chr1 >> 2;

      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);

      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);

      enc4 = chr3 & 63;

      if (isNaN(chr2)) {

        enc3 = enc4 = 64;

      } else if (isNaN(chr3)) {

        enc4 = 64;

      }

      output = output +

        _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +

        _keyStr.charAt(enc3) + _keyStr.charAt(enc4);

    }

    return output;

  }



  // public method for decoding

  this.decode = function (input) {

    var output = "";

    var chr1, chr2, chr3;

    var enc1, enc2, enc3, enc4;

    var i = 0;

    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

    while (i < input.length) {

      enc1 = _keyStr.indexOf(input.charAt(i++));

      enc2 = _keyStr.indexOf(input.charAt(i++));

      enc3 = _keyStr.indexOf(input.charAt(i++));

      enc4 = _keyStr.indexOf(input.charAt(i++));

      chr1 = (enc1 << 2) | (enc2 >> 4);

      chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);

      chr3 = ((enc3 & 3) << 6) | enc4;

      output = output + String.fromCharCode(chr1);

      if (enc3 != 64) {

        output = output + String.fromCharCode(chr2);

      }

      if (enc4 != 64) {

        output = output + String.fromCharCode(chr3);

      }

    }

    output = _utf8_decode(output);

    return output;

  }



  // private method for UTF-8 encoding

  var _utf8_encode = function (string) {

    string = string.replace(/\r\n/g, "\n");

    var utftext = "";

    for (var n = 0; n < string.length; n++) {

      var c = string.charCodeAt(n);

      if (c < 128) {

        utftext += String.fromCharCode(c);

      } else if ((c > 127) && (c < 2048)) {

        utftext += String.fromCharCode((c >> 6) | 192);

        utftext += String.fromCharCode((c & 63) | 128);

      } else {

        utftext += String.fromCharCode((c >> 12) | 224);

        utftext += String.fromCharCode(((c >> 6) & 63) | 128);

        utftext += String.fromCharCode((c & 63) | 128);

      }



    }

    return utftext;

  }



  // private method for UTF-8 decoding

  var _utf8_decode = function (utftext) {

    var string = "";

    let i = 0;

    let c = 0;

    let c1 = 0;

    let c2 = 0;

    while (i < utftext.length) {

      c = utftext.charCodeAt(i);

      if (c < 128) {

        string += String.fromCharCode(c);

        i++;

      } else if ((c > 191) && (c < 224)) {

        c2 = utftext.charCodeAt(i + 1);

        string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));

        i += 2;

      } else {

        c2 = utftext.charCodeAt(i + 1);

        c3 = utftext.charCodeAt(i + 2);

        string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));

        i += 3;

      }

    }

    return string;

  }

}

module.exports = {
  Base64: Base64
}